Marine Birds: Diversity

• Diversity, taxonomy

• Feeding strategies (4)

• Salt gland

• Reproductive strategies

– Colonial breeding

• Migrations

Marine Birds: Diversity

• Seabirds:

– Four major groups

– obtain nearly all food from sea

• Shorebirds, ducks, loons, grebes:

– marine realm provides critical habitat

Seabirds: four groups

Penguins (18 spp.)

Petrels (albatrosses, petrels, shearwaters)

Pelicans (includes boobies, gannets, cormorants)

Gulls, terns, and auks

Seabirds: feeding strategies

1. Plunge divers

• Terns, pelicans, gannets, boobies

• Surface to 1 m depth

• Gannets: up to 10 m depth

• From height of 10-100 m

Seabirds: feeding strategies

2. Feed at surface: Scavengers, planktivores, piscivores

• Pluck: skimmer, storm petrel, fulmar, gulls

• Strain: prion

Seabirds: feeding strategies

3. Kleptoparasitism

• Frigate birds, skuas, some gulls

Seabirds: feeding strategies

4. Underwater swimming

• Dive from surface: to 5-20 m depth

• Penguins: 200 m depth, 10 minutes

• Swim with feet: cormorants, loons

• Swim with wings: auks, penguins, puffins

Seabirds: feeding strategies

• Trade-offs for underwater swimming:

– with wings: can’t fly

– with legs: can’t walk

Seabirds: salt glands

• Secretes salt, brine

• Size, excretion rate depends on life style

• Largest: Albatrosses, petrels

Seabirds: reproductive strategies

• High investment strategy!

– Small clutches: 1 to few eggs

– Large eggs

– Long nestling period

– Late maturity: > 4 yrs

– Monogamous

• Why?

Seabirds: reproductive strategies

• 98% breed in colonies

• Islands

• Coastal rock promontories

• A few to millions of pairs

• Natal site imprinting

• Why?

– Predators?

– Food?

Colony breeding: advantages?

• Predator-safe sites: Limited

• Communal defense

• Sites near food sources: Limited

• Information center hypothesis

Colony breeding: Disadvantages

• Competition

– Food

– Guillemot chicks weight vs. colony size

Colony breeding: Disadvantages

• Competition

– Nest sites

– Nest material

– Mates

• Attract predators

• Spread parasites

Colony breeding: consequences

• Vulnerable to human exploitation

– Great Auk: extinct 1840

– N. Atlantic islands

– Flightless

– Taken by sailors

• Vulnerable to human disturbance

– Predators introduced to islands

• Consequences: Colony sites

• Underwater swimmers

– upwelling zones

– coastal zones

• Good fliers:

– Colonies on tropical islands

– Long migrations to find richer food sites outside breeding season

Seabirds: migrations

• Wanderers

– shearwaters

Seabirds: migrations

• Directed migration

– Arctic tern

Shorebird migration

• Red Knot

• Winters: Tierra del Fuego

• Breeds: Arctic

• Critical habitat

– Grays Harbor WA, Copper River AK

– Delaware Bay